Dave Harris wrote:
I too have a strong antipathy to macros. I don't reject them absolutely, but they need a very good justification. I can't see myself ever using BOOST_FOREACH because the problem it is solving isn't hard enough to warrant the obfuscation. Comparing:
BOOST_FOREACH( int i, vec ) cout << i;
with:
for (iterator i = vec.begin(); i != vec.end(); ++i) cout << *i;
the macro just doesn't seem worth it.
In this simple example, I might agree with you. But see my reply to Gennadiy for an example of something that BOOST_FOREACH can do that an ordinary for loop, or even std::for_each, cannot.
I have looked at the documentation and found it a bit superficial. For example, I can't tell whether the example above is actually supported. All the examples in the documentation have braces around the loop body: are those just the author's preferred style, or are they required by the macro? I looked at the implementation and I still can't tell. I prefer to omit braces when they are not required.
Braces around the loop body are not required. I could add that to the docs.
I have not tried to use the macro. From the source, it looks like it injects a largish number of local variables into the code, and these will show up in the debugger and need to be understood to follow how the loop is progressing.
It injects 5 local variables. I haven't checked, but I suspect that some can be optimized away sometimes. I'm not sure why users will need to understand how FOREACH uses its hidden variables. Can you explain?
For what it's worth, I think the design is impressive and if I had come up with it I'd be very proud. Congratulations. The problem is that it is too clever. It is using a sledgehammer to crack a nut.
This nut is an exceptionally tough one to crack. ;-) -- Eric Niebler Boost Consulting www.boost-consulting.com